flashproxy facilitator: Allow clients to specify transports
The idea of being able to connect flashproxy clients to relays that support specific transports has occured in many places, like comment:5:ticket:7944 comment:2:ticket:5578 and lately comment:17:ticket:7167.
This would allow clients to speak obfs3-over-websocket
instead of the current websocket
protocol.
To accomodate this, clients should be able to signal to the facilitator that they need bridges that support specific transports. The facilitator should be able to search its database for such bridges and point its users to them.